NUnit vs. xUnit vs. MSTest (With Examples)

Posted Oct 24th, 2022

This article compares and contrasts the three most popular unit testing frameworks in ASP.NET Core: NUnit, xUnit, and MSTest.

What is Unit Testing?

Unit testing has been around since the beginning of software testing. Unit testing lays the groundwork for the rest of your software delivery and testing pipelines, making it one of the most crucial phases of the software development lifecycle.

Unit testing entails writing code that examines other blocks of code to ensure that they work as intended. Unit tests examine the most fundamental unit of any application. Only after you have mastered unit testing can you move on to other types of testing – like performance testing, visual testing, and integration testing. 

Unit testing typically necessitates the use of unique unit testing frameworks for each programming language and framework. The three most popular unit testing frameworks in ASP.NET Core, for example, are NUnit, xUnit, and MSTest. These frameworks differ significantly in terms of features and implementation.

Most developers want to know which frameworks work best in which situations and how to choose the best one for their specific C# code. This article compares and contrasts the NUnit, xUnit, and MSTest frameworks.

What Is NUnit?

Adapted from JUnit,NUnit is a free unit testing framework for all .NET languages. NUnit was released under the MIT license and is entirely open source. Although the first iteration of NUnit was a port ofJUnit, version 3 has been entirely rewritten from the ground up with several new features and support for a number of .NET platforms.

NUnit works by isolating the entire application into distinct modules. Each module is independently tested to ensure that the goal is met. The static methods of NUnit's custom attributes and the Assert class’s rich set of assertions make it easy to create unit test cases. Custom attributes of NUnit test runners indicate the presence of unit testing code in these classes or functions. Assert classes, on the other hand, are used to determine whether or not the block of code under review meets a predetermined condition. If an assertion fails (i.e., the condition is not met), the assertion method call does not return, and an error is generated to indicate that the test failed. Custom attributes include TestFixture, SetUp, TearDown, Test, Category, Ignore, TestCase, Repeat, MaxTime, and so on.

What Is xUnit? is a community-focused, free, and open source unit testing tool for the .NET frameworks. It was written by the creators of the NUnit framework, James Newkirk and Brad Wilson, and it’s licensed under the Apache 2 OSI. When it comes to unit testing, xUnit works well with Xamarin, ReSharper, CodeRush, TestDriven.NET, and Console Runner. The “x” in xUnit refers to the programming language for which the framework was created – for example, we have JUnit (for Java code), NUnit (for C#, VB.NET, and other .NET languages), CppUnit (for C++), and PyUnit (for Python).

xUnit is designed in such a way that it allows you to control your tests by adding new attributes. It adds custom functionality to the Assert class by extending the Contains, DoesNotContain, Equal, NotEqual, InRange, and NotInRange methods. It also supports two types of unit tests that use [Fact] or [Theory] annotations to test assertions. The test runner uses the [Fact] attribute to identify a “normal” unit test that is always true (a test method that takes no method arguments and tests invariant conditions). Meanwhile, [Theory] annotation tests accept multiple inputs and are true for a specific set of data. By default, xUnit runs all tests in separate class files in parallel. This allows us to run our tests in parallel without any special configuration.

What Is MSTest?

MSTest is a unit testing framework that was developed by Microsoft and integrated into their Visual Studio IDE. There is also an open source version called MSTest V2, which is now available fordownload from This allows you to assess the code by using a wide range of attributes at the method and class levels instead of using external tools.

The main features of MSTest V2 are:

  • It’s open source – The MSTest V2 project isopen source and hosted on GitHub. Its open repositories areMicrosoft/testfx andMicrosoft/testfx-docs.

  • It provides cross-platform support – MSTest V2 allows developers to create tests for the .NET Framework, .NET Core, and ASP.NET Core on Linux, Mac, and Windows.

  • It enables data-driven testing – By enabling data-driven testing, MSTest V2 allows users to specify the behavior of their tests. This way, a single method can be executed multiple times by passing different input arguments.

  • It supports parallel test execution – MSTest V2 supports parallel test execution, which speeds up the whole process. In-assembly parallel test execution makes it possible to run tests concurrently via RunSettings or annotations. 

  • It enables customization through annotations – The MSTest V2 framework allows you to customize the test execution lifecycle through annotations like [TestClass], [TestMethod], [TestInitialize], and [TestCleanup].

  • It’s extensible – Its features can now be extended with unique test attributes and unique assertions, just like other test frameworks.

NUnit vs. xUnit vs. MSTest: Feature Differences

The three most popular .NET unit testing frameworks (discussed above) each function differently by providing testing teams with various features. In this section, we will compare each feature separately.

Criteria NUnit Test xUnit Test MSTest V2
Grouping Tests by Class [TestFixture] Not Available [TestClass]
Test Setup and Teardown
(Note: The setup method takes a constructor, while a teardown needs an IDisposable interface.)
Not Available [TestInitialize]
Single Test Case Declaration [Test] [Fact] / [Theory] [TestMethod]
Multiple Data Test Cases Declaration [TestCase] [Theory]
Repeat Initialization for Each Test [SetUp]
[Ctor], [IDisposable] [TestInitialize]
One-Time Initialization for All Tests in One Class [OneTimeSetUp]
[MethodMember] or [PropertyMember]
One-Time Initialization for All Tests in One Assembly Dedicated class with [SetUpFixture] + [OneTimeSetUp] [OneTimeTearDown] [MemberData] Or [ClassData],[PropertyMember] [TestClass] + [AssemblyInitialize] [AssemblyCleanup]
Execution in Isolation
Configurable Default support Default support
Skipping a Test
[Fact (Skip=” reason”)] [Ignore(“reason”)] [Ignore]
Comprehensive and well-maintained documentation.

Available here.
Does not have well-maintained documentation.

Available here.
Comprehensive and well-maintained documentation.

Available here.

NUnit vs. xUnit vs. MSTest Code Examples

Sample NUnit Test

Below is a sample test case that starts a browser locally, executes a very simple test using NUnit and Chrome web drivers, and then closes out the browser instance. You can view the complete tutorial here.

using NUnit.Framework;
using OpenQA.Selenium;
using OpenQA.Selenium.Chrome;
using OpenQA.Selenium.Support.UI;
namespace WebDriver_CSharp_Example
    public class Chrome_Sample_test
        private IWebDriver driver;
        public string homeURL;
       [Test(Description="Check SauceLabs Homepage for Login Link")]
        publicvoidLogin_is_on_home_page() {
            homeURL = "";
            WebDriverWait wait = new WebDriverWait(driver, 
            wait.Until(driver => 
            IWebElement element = 
            Assert.AreEqual("Sign In", element.GetAttribute("text"));
            homeURL = "";
            driver = new ChromeDriver();

Sample xUnit Test

The following is a sample unit test written using the xUnit framework in C# to validate arithmetic methods of addition and multiplication:

public class MathUnitxTest
        public void Task_TestAddition()  
            var numA=12, numB=4, result=16; 
            var calculatedSum = MathOperation.Add(numA, numB);  
              Assert.Equal(expectedValue, calculatedSum, 1);  
        public void Task_TestMultiplication()  
            var numA=5, numB=4, result=20; 
            var calculatedOutput= MathOperation.Multiply(num1, num2); 
            Assert.Equal(result, calculatedOutput, 2);  

Sample MSTest Test

The following is a sample unit test written using the MSTest framework in C# to validate arithmetic methods of addition and subtraction:

namespace Messages.Tests;
using Microsoft.VisualStudio.TestTools.UnitTesting;

public class ArithmeticMsTest
    [DataRow(1, 2, 3)]
    [DataRow(2, 2, 4)]
    [DataRow(-1, 4, 3)]
    public void Task_TestAddition(int x, int y, int expected)
        int sum = Basic.add(x, y);
        Assert.AreEqual(sum, expected);
    [DataRow(1, 2, -1)]
    [DataRow(2, 2, 0)]
    [DataRow(3, 2, 1)]
    public void Task_TestSubtraction(int x, int y, int expected)
        int res = Basic.sub(x, y);
        Assert.AreEqual(res, expected);

NUnit vs. xUnit vs. MSTest: Which Should You Choose? 

The Xunit, Nunit, and MSTest .NET frameworks have all evolved over the last few years. For instance, compared to MSTest V1, MSTest V2 offers significantly improved usability and compatibility with other tools. With their developers offering more community-focused support, the xUnit and NUnit frameworks have also grown more sophisticated.

Ultimately, all three frameworks provide features and tools that enable elaborate unit testing. Based on the above comparison of their distinguishing features, you can see that it comes down to personal preference. If we had to choose a favorite, we would pick NUnit due to its straightforward naming conventions for attributes and assertions. It can also be used along with Selenium and web drivers to run a variety of automated unit tests – including cross-browser testing.

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